In wavelength division multiplexing (WDM) based optical networks such as course WDM (CWDM) networks, different wavelengths are assigned to different WDM channels for distributing data along e.g. an optical ring network. The various WDM channel signals may be added and/or dropped at individual network nodes connected in-line on the optical ring network for distributing and receiving data to and from subscribers.
It has been proposed in such CWDM networks to design the network nodes in a manner which enables each WDM channel to carry data of a different protocol, e.g. different speed data protocols. Furthermore, it has been proposed to design such CWDM networks in a manner which enables different wavelength channels to be selectively added or dropped at individual network nodes, as opposed to fixed wavelength(s) being added or dropped at individual network nodes based on an initial network design. Yet further it has been proposed to design such CWDM networks in a manner which enables each individual CWDM channel to be transmitted in pairs of wavelengths in different directions along the optical ring network if required to e.g. implement a single path protected channel.
However, while such proposals seek to provide a highly flexible and upgradable optical network design, it has been recognised by the inventors that such a network design results in high entry costs for the deployment of an optical network, which may render such network designs unsuitable for competing with or breaking into the existing electrical or optical communication networks market.
In at least preferred embodiments, the present invention therefore seeks to provide CWDM network node modules offering reduced entry costs in the deployment of optical networks.